Acute kidney injury criteria predict outcomes of critically ill patients*

Abstract

The Acute Kidney Injury Network's proposed definition for acute kidney injury (increment of serum creatinine ≥0.3 mg/dL or 50% from baseline within 48 hrs or urine output 6 hrs despite fluid resuscitation when applicable) predicts meaningful clinical outcomes. Retrospective cohort study. A 350-bed community teaching hospital. The study population consisted of 471 patients with no recent history of renal replacement therapy who were admitted to the medical intensive care unit during 1 yr. Medical records of all patients were reviewed using a data abstraction tool. Demographic information, diagnoses, risk factors for acute kidney disease, physiologic and laboratory data, and outcomes were recorded. Of 496 patients, 471 were not receiving renal replacement therapy in the weeks before medical intensive care unit admission; 213 had changes ≥.3 mg/dL in serum creatinine within 48 hrs and/or urine output of ≤.5 mL/kg/hr for >6 hrs. Detailed fluid challenge information was available for only 123 patients, who met acute kidney injury criteria, and three patients reversed after administration of ≥500 mL of intravenous fluid and/or blood products. All patients whose creatinine increased ≥50% also had increments ≥0.3 mg/dL. The 120 patients with acute kidney injury were older (mean ± se: 69.3 ± 1.7 vs. 62.9 ± 1.3, p < .01), were more ill (Acute Physiology and Chronic Health Evaluation II score 18.7 ± .6 vs. 13.3 ± .4, p < .01), and had multiple comorbidities (two or more organs, 65% vs. 51.3%, p < .01) compared with those without acute kidney injury. The mortality rate of patients who met criteria for acute kidney injury was significantly higher than that of patients who did not have acute kidney injury (45.8 vs. 16.4%, p < .01). In multivariate logistic regression analyses, acute kidney injury was an independent predictor of mortality (adjusted odds ratio 3.7, 95% confidence interval 2.2–6.1). Acute kidney injury was a better predictor of in-hospital mortality than was Acute Physiology and Chronic Health Evaluation II score, advanced age, or presence of nonrenal organ failures. Median hospital stay was twice as long in patients with acute kidney injury (14 vs. 7 days, p < .01), and only patients with acute kidney injury required hemodialysis during hospitalization. The oliguria criterion of acute kidney injury did not affect the odds of in-hospital mortality. The Acute Kidney Injury Network definition of acute kidney injury predicts hospital mortality, need for renal replacement therapy, and prolonged hospital stay in critically ill patients. An increment of serum creatinine ≥0.3 mg/dL in 48 hrs alone predicts clinical outcomes as well as the full Acute Kidney Injury Network definition.